Ms Duffield has written to senior county councillors outlining parents’ concerns.

In her letter, she said: “Many parents have been moved to contact me out of desperation.

“Whilst I appreciate that the costs of any service increases as times goes by, I have been advised that the price of a Young Person’s Travel Pass has risen year on year without consultation or explanation.”

Parent Carolyn Mills agreed with Ms Duffield’s stance on the issue.

She said: “For the last two years I had to pay £400 each year for my son to get to college and back, it’s ridiculous. I had to save up over four months to get that money.”

Kent County Council has described itself as being in the “unenviable position of having to put the cost of the pass up”.

The authority insists that its subsidised scheme was among the most generous in the country.

It added that it does not have to provide subsidised travel, but does so because it is committed to encouraging sustainable transport.

And not everyone agrees with subsidised travel.

Responding to Ms Duffiel’s letter, Steve Harris said: “Nobody should get anything for free, no subsidies, no schemes, then when nobody buys their overpriced tickets they will be forced to charge a market rate.”